In an effort to require power plants to install and use "readily available technologies to remove pollutants before they are released into waterways," EPA is planning to propose new limits on the quantity of toxic metals in coal-fired power plants effluent. Heavy metals are captured by air pollution scrubbers that remove sulfur dioxide and are found in coal ash storage ponds (where power plants store the leftovers of burning coal). EPA is targeting heavy metals such as selenium, cadmium, mercury and lead, claiming that the current regulations do not control these metals, and do not protect water quality and wildlife. EPA is planning to unveil the new rules in 2012. This issue was brought to the forefront by last year's spill at a coal ash pond in Tennessee that flooded hundreds of acres of land, damaged homes and killed fish in nearby rivers. Following the spill, three environmental groups threatened to sue the EPA for failing to update its regulations.